Oct. 8, 1940. . H, FgCKE » 2,217,106 ROTOR FOR RÖTATING-WING Filed Feb_. 18, 1938. Patented Oct. 8, 1940 ' _ 2,217,106

UNITED -sTATl-:s- PATENT ol-‘FlcaA

Henrich Focke, , ApplicationFebruary 18, 1938, Serial No. 191,327 I » In Germany August 16, 1937 6 Claims. (Cl. 244-18) 'I'his invention concerns rotor devices for ro trated being extended from the main spar. The tating-wing aircraft, of the kind comprising a tips of the consecutive columns or `arms b are plurality of blades jointed to the hub. connected by tension'­ members c one carried An important object of the invention is to pro forward to each preceding blade in the dire‘c 5 vide interconnections adapted for inñuencing tion of rotation indicated by the arrow A and 5 the rotor blades in such manner that the latter one carried rearwardly to each following bladeA will constantly tend to maintainprecise angular and connected in a similar manner thereto. The intervals between themselves. blade a which is jointed to the hub by the uni The blades of air-screws have 4been braced tof versal joint e, ispas shown in Figure 2, also 10 gether in order to maintain their angular posi mounted in a bearing sleeve f so as to be rotat- 1. tions. For example, a. bracing of this kind was able about the axis of its spar. Thus, in the provided by Oehmichen (France) in his heli revolutions of the >rotor around the vertical or copter No. 3 of the year 1928. ' lifting axis g, each blade is capable of making Furthermore, it is known to provide ties for an overtaking or a lagging movement or a. ñap vl5 interconnecting the blades of a lifting screw, ping movement due to the provision of the uni 15 the eiîect of these ties being to maintain the versal jointe, or a rotational movement abr-.it angle of incidence of the blades as well as the , the axis of the spar due to its mounting in the angular intervals between them. In this ar sleeve f. The rotational movement, however, is rangement, fittings for the attachment of -ties >limited by the springs i‘i which are suitably 20 extending forwardly from the blades, were of a anchored at their lower ends and connected at 20 _ height different from that of ñttings for the at­_ their upperA ends with the extremities of a two tachment of ties extending rearwardly from the armed vlever h. Thus, the blade always tends to

blades. ' ' ` assume a certain angle of incidence which is In order to ensure balanced running of the determined by the tensioning of the springs i i. 25 rotor it is essential constantly to ensure the pre In operation, if the blade a lags relatively to 25 cision of the angularsetting o! the blades be its preceding blade in the direction of revolution tween themselves, and no solution ofthe prob A, then the tension of the member c is increased, lem involved is to be found in the arrangements either immediately, or after the execution of a previously proposed. , small lagging movement if the member c was not 30 The problem, however, is solved lby the presen previously tensioned. Under the pull of the 30 ' invention which utilizes varyingtension in the member c the column b is tilted forwardly blade interconnections for influencing the angles` thereby turning the blade and its mounting in of incidence of the several blades so that the the sleeve f and reducing the incidence of the latter have the above-stated tendency, namely, blade. Owing lto the consequent reduction of 35 constantly to maintain precise angular intervals air resistance on the blade, the latter now ac- 35 vbetween themselves. Thus, for example, if a celerates and overtakes, thereby re-establishing blade lags in the direction of rotation, its angle the required conditions. If, on the other hand, of incidence is reduced by the pull of an inter the blade a initially overruns. then the tension connection, thereby reducing the air~ resistance „member d becomes tensioned to cause a reverse 40 on this blade and enabling it to overtake. If a tilting of the column b and a consequent increase 40 blade overruns, the converse takes place with in the angle of incidence of the blade. The re the result that the blade in question has a degree sultant increase in air resistance on the blade of lag. - then causes the latter to lag, so 'that again the VFurther features `of the invention will appear required condition is restored. 45 from the following description having reference Instead of rotatably mounting the blade by 46 to the annexed drawing wherein, Figure l‘illu's means of the bearing sleeve f and employing trates one constructional example in perspective springs i i for adjusting the bladerotatively as and more or less diagrammatically and Figure 2 in Figure 2, in some cases the natural torsional discloses a further embodiment thereof. elasticity of the blade and its spar may sumce 50 In the drawing', blades a of a rotor -are shown for obtaining a similar eifect. Such construction 50 partly broken away for sake of clearness. Each is illustrated in Figure 1. ` blade a which may be built up on a main tubu- « lar spar and ribs, has a column or arm b,­ pref 1. A rotor for type aircraft compris erably of stream-lined shape, mounted upon it, Y ing in combination, a hub„~ a plurality oi blades 5_5 the said column or arm inthe examples illus radiating from said hub, said blades being con

i. 2,217,106 structed for adjustment of incidence angle, a blade mountings on the rotor hub so adapted that drag joint betweeneach blade and the hub where the incidence of the blades can be adjusted by by blade spacing' may be varied by unequal lag natural torsional ilexibility thereof, drag joints ging or leading oi' the blades, a blade tilting between the blades and hub, a crank arm rigidly arm on each blade and means connecting each mounted ‘on each spar beyond the drag joint, arm to the arms of the preceding and succeeding and upstanding from'the blade, and tensional blades whereby the angle of incidence of a mis interconnections between adjacent arms. placed blade is changed until it regains its proper 5. A rotor for helicopter type aircraft compris spacing. l . 10 2. A rotor for helicopter type vaircraft com ing in combination, a hub, a plurality of blades, means pivoting each blade to said hub for ro'ta 10 prising in combination, a hub, a plurality of blades tion to adjust the angle of incidence thereof, radiating from said hub, said blades being con spring means connecting each blade and hub and structed for adjustment­ of incidence angle, a tending constantly to preserve a predetermined drag joint between each blade and the hub where 16 by blade spacing may be varied by unequal lag angle of incidence, a drag joint for each .blade ging or leading of the blades, means associating outwardly of said pivoting means, an arm extend 15 each blade with the contiguous blades, said means ing upwardly from each blade, and a tension being constructed to change the angle of incidence member connecting the upper end of each arm of any blade upon a change of its spacing with tothe upper end of the arm of the preceding respect to said contiguous blades. blade. i " ï 3. A rotor for helicopter type aircraft com 6. A rotor for helicopter type"`aircraft com 20 prising in combination, a hub, a plurality of prising in combination, a hub, a plurì'ablity>~ of blades, means joining each blade to the hub for blades, means pivoting each blade to said hub for rotation thereof to change the angle of incidence, rotation to adjust the >angle of incidence thereof,” ‘ a dra'g joint between each blade and the hub spring means connecting each blade and hub and permitting unequal blade spacing, an arm on each tending constantly to preserve a predetermined blade outwardly of all joints and extending up angle of incidence, a drag joint for each blade ward from the plane of rotation thereof, and a outwardly of said pivoting means, an arm ex 30 tension member connecting the end of each arm tending upwardly from each blade, a tension to the end of the arm on the preceding blade member» connecting the upper end of each arm 30 whereby any change of blade spacing produces to the upper end of the arm of the preceding va change of the angle of incidence of the affected blade, and means to simultaneously adjust the blade. y lsaid predetermined angle of incidence of al1 35 4. In an aircraft rotor comprising blades each blades. built up on a main longitudinal spar, a rotor hub, HENRICH FOCKE. 35